This invention relates to the detection of antibodies and antigens and to vaccines and methods for immunizing against disease. More particularly, the invention relates to the production and propagation of a known virus and the use of that virus to induce antibody formation and the subsequent immunization of hosts especially humans against both type A and type B viral hepatitis. Specifically, it relates to the use of virus-derived materials in the prevention of type A and type B hepatitis, and to methods for detecting the presence of hepatitis B core antigen and antibody and hepatitis A antigen and antibody.
Hepatitis is a viral disease well known and frequently encountered in everyday life. The disease is intractable and is characterized by inflammation of the liver, jaundice, fever and other systemic manifestations. There are two types of hepatitis generally recognized, the so-called type A and type B, each of which is associated with a different virus.
The virus associated with type B viral hepatitis has been identified immunologically as Australia Antigen (HAA). Type A hepatitis is associated with a virus characterized simply as Hepatitis A Antigen. For purposes of shorthand notation and convenience of reference, Hepatitis A Antigen is frequently written as HAAg and Hepatitis B Antigen is commonly designated as HBAg.
The disease caused by each of these organisms is virtually clinically identical. While there may be some differences in incubation periods, the course of the disease generally follows the same clinical path. Initially, the infected patient may encounter headache, nausea, muscle cramps, fever, chill, fatigue and a general malaise. These symptoms can vary as to severity in individual patients, but are usually followed by what is known as the icteric phase of the disease wherein jaundice begins. The onset of the icteric phase usually comes somewhere between 29 and 100 days following infection depending on the species type of causative organism.
Antigen from Type B hepatitis (HBAg) in infected patients can usually be found in the serum, and often in the semen, saliva and urine of those patients. On the other hand, antigen from patients infected with A type hepatitis (HAAg) is found in the feces of those patients.
HBAg and HAAg are distinguishable under the electron microscope, especially by the technique known as immuno-electron microscopy (IEM). On that level, the A Antigen appears as particles roughly in the shape of icosohedrons, varying in size from approximately 25 to 30 nanometers (nm.). The hepatitis B virus is presently recognized as comprising a mixture of particles called Dane Particles and debris from the surface of the Dane Particle.
The Dane Particles are spheres which contain a coat protein covering a core particle generally the shape of an icosohedron. The Dane Particle spheres are generally observed in the 40 to 45 nm. size range, whereas the core of the Dane Particle appears in the range of approximately 27 to 30 nm. The debris from the Dane Particle spoken of above is usually comprised of disrupted parts of the coat or surface protein and is generally manifested in the form of spheres and tubules usually in the 20 to 25 nm. range. In hepatitis caused by hepatitis B virus, it is the core material of the Dane Particle which is the presumptive infective agent.
Still with reference to the Dane Particle, the coat surface protein thereof is designated as HB.sub.surface Ag (also HB.sub.s Ag) while the core material is designated HB.sub.core Ag (also HB.sub.c Ag). It is important to note that the Dane Particle surface protein (HB.sub.s Ag) and the debris represented in the B antigen are antigenically similar. That is, HB.sub.s antigen cross-reacts with antibodies produced from the debris of hepatitis B antigen. On the other hand, the Dane core particle (HB.sub.c Ag) is antigenically discrete from the Dane surface protein (HB.sub.s Ag). That is, HB.sub.c Ag will not cross-react with antibodies induced by HB.sub.s Ag. Similarly, HB.sub.c Ag will not cross-react with HB.sub.s Ab. (For purposes of shorthand notation, it is common in the art to designate the antibodies simply as, for example, HB.sub.s Ab). When the terms HBAg or HBAb are used in the literature, the designation usually means HB.sub.s Ag or HB.sub.s Ab. That is, it is the surface antigen of the Dane Particle and/or the debris of the B antigen that is usually referred to. This is especially true of literature appearing before 1974, when the distinction between core antigen and surface antigen was not fully appreciated. Currently, the recommended nomenclature for antigens associated with viral hepatitis type B promulgated by the U.S. National Academy of Sciences - Committee of Viral Hepatitis of the National Research Council is as follows:
Cytoplasmic hepatitis B antigen (CHBAg) corresponds to hepatitis B surface antigen (HB.sub.s Ag), while nuclear hepatitis B antigen (NHBAg) corresponds to hepatitis B core antigen (HB.sub.c Ag). Antibody to CHBAg (CHBAb) corresponds to antibody to HB.sub.s Ag (anti-HB.sub.s), while antibody to NHBAg (NHBAb) corresponds to antibody to HB.sub.c Ag (anti-HB.sub.c).
As stated above, the presumptive causative organisms of viral hepatitis are two: HB.sub.c Ag from hepatitis B virus and HAAg from hepatitis A virus. There is no core or surface distinction for hepatitis A Antigen, since the form of this particle is entirely different from that of the B virus. Immunologically, antibodies induced by B Antigen will not cross-react with A Antigen. Similarly, antibodies induced by A Antigen will not cross-react with B Antigen.
The importance of this will readily be understood by one skilled in the art. In order effectively to provide immunization against the onslaught of a viral attack, one would have to provide within a host an antigenic substance capable of inducing antibodies which would cross-react with the virus (i.e. the antigenic substance) involved in the attack. Therefore, in order to induce antibodies against hepatitis A virus, one would normally have to first induce in the host the formation of hepatitis A antibody. This would have to be accomplished by administering an antigenic substance capable of inducing those antibodies. The same may be said of the approach to preventing infection by hepatitis B virus. To date, no one has been able to produce a type A Antigen or type B Antigen outside of a host and for administration in an immunization procedure, and this has frustrated attempts at obtaining effective vaccine production.